The present invention relates to so-called “Personal Aircraft” (“PAC™”) which is capable of vertical take-off and landing (“VTOL”). Such an aircraft is operable to carry a relatively light payload (for example, 600 pounds which is the equivalent of two or three people) for short distances (for example, 250 miles) at relatively slow cruising speeds (for example, 50 to 100 MPH).
A Personal Aircraft of this type is disclosed in the International Patent Publication No. WO 03/029075 A2, which is incorporated herein by reference. It is characterized by the use of ducted fans, instead of rotary helicopter “wings”, to generate lift while hovering. In this prior art design, a plurality of ducted fan units (each including an impeller and an engine, surrounded by a ducted fan tube) are arranged in the aircraft wings which extend outward in both directions on either side of the fuselage. At least one ducted fan unit is arranged on each side of the aircraft. Due to the wings, this aircraft has a relatively large “footprint”, and cannot squeeze into small spaces during flight.
Another design of a Personal Aircraft is disclosed in the U.S. Pat. No. 6,464,166, which is incorporated herein by reference. This aircraft incorporates two ducted fan units, both in the fuselage, with their axes of rotation arranged along the centerline of the fuselage. This aircraft has no wings at all, so that it has an extremely small footprint and can fly through narrow passages, such as city streets. However, due to this absence of wings, the ducted fans must generate all of the lift to maintain the aircraft aloft. Consequently, this type of aircraft is not particularly fuel-efficient in transporting a payload from point A to point B.
Still another design of a Personal Aircraft is disclosed in the U.S. Pat. No. 5,454,531, which is incorporated herein by reference. This patent discloses a primary and two secondary (control) ducted fan units arranged in a fuselage. Short, stubby wings are arranged on opposite sides of the fuselage to provide lift during high-speed flight. This aircraft also includes a canard in front with trailing control surfaces and a horizontal stabilizer in back, also with a trailing control surface. In addition, the aircraft includes two rudders with vertical trailing control services.
Still another aircraft design is disclosed in the U.S. Pat. No. 5,115,996, which is incorporated herein by reference. This aircraft incorporates four ducted fans, two on each side of the fuselage in front and two on each side in the rear for both vertical and forward propulsion. Both the fuselage and the ducted fans are configured to jointly form an aerodynamic lifting body which cooperates with a horizontal stabilizer to provide aerodynamic lift to the aircraft in forward flight. As in the case with the aircraft disclosed in the aforementioned U.S. Pat. No. 5,454,531, this aircraft has an extremely low lift-to-drag (L/D) ratio at moderate speeds (below 100 MPH). This aircraft is designed for relatively high speeds (far in access of 100 MPH) and, as a result, it is not at all fuel efficient in traveling from point A to point B in the 50-100 MPH flight regime.
Several aircraft are known which incorporate wings of adjustable size. The U.S. Pat. No. 4,824,053 discloses an aircraft having wings which are telescopically extendable to adjust its wingspan (the distance from wingtip to wingtip). The U.S. Pat. No. 4,471,928 discloses an aircraft with wings which are telescopically adjustable in width. Both of these U.S. patents are incorporated herein by reference. According to the patents, both the length and contour of an aircraft wing can thus be adjusted to match the requirements of flight.